As a conventional technique, for example, according to Patent Literature 1 mentioned below, in a plurality of power conversion devices that are connected in parallel to an AC power supply and are operated, a phase angle that minimizes harmonics leaked to the side of the AC power supply is set in each of the power conversion devices, and a carrier waveform is generated while considering the phase angle using a zero point of a sinusoidal wave of a power supply voltage as a reference.
Further, according to the Patent Literature 1, all of the power conversion devices in a consist are handle as equivalent devices, and when phase differences are given to the carrier wave to suppress harmonics, the angles thereof are set at equal intervals.